August 24th

Hi All,

Well this will be the last blog for August and for a couple of weeks as next week is bank holiday here and the week after I’m off to hopefully say “Bore Da” to some Bass in North Wales with my fly gear as well as catch up with some sleep and waves hopefully :). I’ve never caught a saltwater species (in this country) on a fly so that’s my objective as long as the weather behaves that is….

Talking about the weather, it doesn’t seem like so long ago we were battling with extreme heat and now some of us have had some pretty extreme rainfall and the temperatures have seemingly settled into autumnal mode. If you think it doesn’t feels like autumn now, you will do by the weekend when we pick up a north westerly airstream and those temperatures drop back even further 🙁 As predicted the jet stream has taken a hike southwards and that has left the way clear for some Atlantic low pressure systems to push across the U.K and Ireland over the next week or so.

I listened to a science broadcast recently that confirmed that the increased incidence of jet stream blocking events (caused by a slowing jet stream) is due to the warming of the polar ice cap with less temperature differential between The North Pole and The Equator. If so, it is indeed a prefect storm because more blocking events in the future will cause more heat to move further north and therefore increase the speed of ice melt. You can read a pretty easy to understand article here

The study also confirmed that the incidence of blocking events is increasing….

For us managing sportsturf this has profound implications, more risk of high rainfall events, prolonged high temperatures with associated E.T and conversely the possibility of some very cold winters thrown into the equation. It sounds like we should invest in water capture / reservoirs, drainage and irrigation as a way forward. Of course these changes are also driving disease incidence and severity and I’ll speak about that later.

Onto this week’s and next week’s weather….

General Weather Situation

Looking at the chart above we look pretty settled today and that’s what we are. There are some showers moving along the M4 / South Coast, west to east but these will fizzle out as we progress through the morning as they head east however they are likely to be joined by more showers later pushing in off The Irish Sea into West Wales, The South West, The South Coast and moving west-east. Away from this southerly rain and some showers over Co. Clare, we look to have a reasonably dry, settled day with lighter winds than of late. No great shakes on the temperature side of things though with mid-teens across Ireland and Scotland and high teens perhaps just nudging the twenties down south. Winds will be light westerlies….

Onto Tuesday and we see the first of this weeks low pressure systems arrive into Ireland bringing with it heavy rain and strong winds. By dawn it’ll already be across half of the U.K and all of Ireland with heavy rain for Ireland and Wales. By contrast the northern half of the U.K will be dull and dry initially on Tuesday morning. During the morning the low will push northwards into the north of England and The Borders with plenty of rain and wind accompanying it. By lunchtime on Tuesday the low begins to clear the south of Ireland and The South West, with the heaviest rain now north of The Humber. Not for long though because the low spins round on its axis and pushes more rain into Ireland before finally clearing the south of Ireland and the U.K during the mid-late afternoon.  In turn Scotland now picks up the brunt of the rainfall with some heavy stuff around over Central Scotland. Winds will be strong to gale force and from the west. Temperature-wise, well not bad with mid to high teens for England and Wales and mid-teens for Wales and Ireland.

Mid-week and overnight that low pressure system is now over The North Sea but it will still be pushing rain into the north east coast of the U.K accompanied by cooler north-easterly winds. Further south, the low pressure will pull in north westerly winds and showers into North Wales and the North Midlands / north of England accompanied by strong winds. Further south it’ll be dry and windy with some reasonable temperatures for the time of year. Ireland looks to have a pretty dry day on Wednesday save for a few showers pushing in across Connacht later in the morning / afternoon. As we progress through Wednesday that rain becomes confined to the north east of England which will have a pretty wet day I am afraid. As we approach the evening we see more in the way of showers across the north west of Ireland and Northern Ireland but across The Irish Sea things should be reasonably dry.

Thursday sees a bit of a silent assassin of a low pressure system push in from The Irish Sea. I say silent assassin because it will come with none of the strong winds normally associated with a low pressure system and it’ll be slow-moving as a consequence. So during Thursday morning we will see rain push into the west of Ireland and move eastwards. By lunchtime it’ll be across Wales and the west of England and moving slowly eastwards reaching central and eastern parts later on Thursday. Scotland will miss most of this rain as the low is southerly-orientated. As we approach dusk we see some sunnier intervals begin to break through across Ireland and the west of England / Wales. A quiet day wind-wise despite the presence of a low pressure system and this will keep temperatures up in the mid to high teens.

Overnight into Friday and that low pressure system has sunk down into mid-France. This will mean the trailing edge will pull over rain on an easterly wind into the south east / north east of the U.K and Ireland. Tricky to say where the worst of the rain will be on Friday because it’s coming in off the continent but at this stage it looks like south of The Humber will be worst-affected.  Ireland will see a wet day as well though the west and east coast may miss the worst of it. Scotland looks to stay dry and dull. As those winds swing round to a north-easterly direction, that’ll pull in cooler air with the low pressure system and keep temperatures down to the mid-teens, a tad cooler than of late !

Not surprisingly the outlook for the weekend is on the cool side with a dominant north / north-east airflow through to the end of the Bank Holiday. Not huge amounts of rain around though with this wind direction there’s always the chance of some showers pushing in off The North Sea to affect the north east and eastern coastline of England. Dull, cool and windy ain’t a great forecast but that’s what we have got. Maybe a chance of more brightness across Ireland and the west of the country later into the weekend / Monday. Temperature-wise in those north easterly winds, no great shakes with mid-teens the norm and maybe just pushing up into the high teens further south during Sunday / Monday as the sun peeps through 🙂

Weather Outlook

As we can see from the GFS projection above, next week sees a deep low pressure system over Scandinavia bringing much-needed rain after a long period of high temperatures and no rainfall for Denmark, Sweden and the like. As you can see Monday doesn’t look too bad and certainly the best day of The Bank Holiday for those that are enjoying one. You may also note a low pressure system lurking across in the Irish Sea and that is due to swing in through Tuesday and bring a south westerly airflow, milder temperatures and of course rain for Ireland initially and then the U.K as well on Tuesday. More showers on Wednesday for the west as we continue to see low pressure affect our weather. During Wednesday / Thursday we see a northerly low push through to bring rain, some of it likely to be heavy for Scotland with showers and a cooler north westerly wind setting towards the end of the week. So cool and unsettled is the weather picture for next week, wetter in the south for the first half of the week and in the north for the second half.

Agronomic Notes

A pretty tricky week last week with the prolonged high humidity and rainfall sparking off lots of disease on turf surfaces.

The picture above is of Thatch fungus, not taken recently, in fact it was taken in the coldest, driest February I can remember. This diverse species of fungus in common with some Fairy Rings fungal species ‘likes’ to decompose organic matter leading to the inevitable green up and ‘dishing’ of the surface. With record high temperatures followed by rainfall, there’s been huge amounts of this disease around really since we got the rain in early June. It can be very destructive to fine turf surfaces and I’ve seen greens where you could roll up the turf above the area of activity in the soil. It does sometimes respond to Azoxystrobin mixed with a wetting agent but really we are dealing with the symptom here rather than the cause, that of organic matter. With many clubs not aerating / topdressing significantly this spring due to Covid-19 and then since opening, they are either too busy to aerate and / or don’t want the disruption understandably, we will see consequences. I believe this disease is one of them but ultimately the main driver is climatic.

 

With the cooler temperatures and rainfall, we are going to see lots of Etiolated growth doing the rounds and sure enough when I was out last week I took this snap from a fine turf area that hadn’t yet been cut. Really at a dead end with this one because unlike the U.S where they have pinned down the causal agents as specific bacterial species, we haven’t seen the same association here. Even if we had, it would mean using a anti-bacterial product (antibiotic) on your surfaces and I don’t think that’s a good road to be going down 🙁

Not the greatest picture of a worm cast, I’m sure you guys could send me many better but undoubtedly the arrival of rainfall after high temperatures has triggered a huge amount of worm activity much earlier than we would normally see it. With Carbendazim long gone now, it isn’t a surprise that we are seeing more worm activity on our surfaces, it is early though and with a wet week this week and next, I’d expect to see plenty of casting on surfaces. There’s nothing legally out there to control them so another frustrating one for groundsman and greenkeepers alike, especially on outfield areas.

Dollar Spot and The Smith Kerns Model….

With the high humidity and temperatures this summer we have seen an increase in Dollar Spot, especially on surfaces with high Fescue and / or Ryegrass. As I wrote about earlier this summer, this disease is on the move so to speak. Originally an outfield disease in Europe, it is now well established as a disease of fine turf across Scandinavia and continental Europe (as well as outfield). Here we see most of the issues on tees, approaches, fairways and the like although some sites have also reported an issue on greens. In the States, Jim Kern and associates developed the Smith Kerns Dollar Spot prediction model and I know a number of you use this not just for Dollar Spot but also for Microdochium nivale in the autumn winter. The model itself uses 3 weather parameters, humidity, minimum and maximum temperature and plugs them into a logarithmic equation. You can read all about it in more detail as well as download the centigrade version of the spreadsheet to use at your site here

Clicking the link above gives you access to a spreadsheet developed by Paul Koch at the University of Winsconsin that looks like this….

If you have a weather station you can plug in your minimum and maximum air temperature data along with the daily humidity and it’ll spit out a number which is visible in the far right column of the file. This is the probability of Dollar Spot occurring. The model assumes no Dollar Spot development below 10°C or above 35°C  and works on a 5-day average humidity exceeding 70% as the tripping point.

Now in the States where Dollar Spot is their No.1 turfgrass disease on greens and outfield, they have developed a system where they will spray a preventative fungicide whenever the probability reaches 20% or more.  Of course over here we don’t really have that option because it is mainly an outfield disease and spraying fungicide on outfield isn’t really a workable solution. Since humidity is the driver and therefore plant leaf wetness is the associated issue that encourages fungal growth (together with temperature) there are things we can do to mitigate this (manual dew removal, dew control, etc)

I did some work with this last year and this year and the results are interesting in terms of the not just probability of Dollar Spot, but also I think other humidity-related diseases like Waitea and Red Thread.

Below is a chart from a location in East Anglia that picks up really high disease pressure from Red Thread on outfield…

So looking at the chart above,  if this was the U.S we would be applying a preventative fungicide every two weeks or so from the 3rd week of May…..Now you know why the chemical companies have such big stands at the GIS !!!!

As explained earlier, we aren’t in that boat but what I have seen is once the probability reaches >60% oat this location, they have extremely aggressive Red Thread on their Rye / Fescue-dominated areas. Now of course the threshold / trigger point will be different for each location and you may not have an issue with this disease or for Dollar Spot . That said it is worth spending some time noting activity dates on these and other diseases and maybe what the Smith Kerns Prediction Model was indicating at the time. For sure going forward we know the fungicides we have are best used preventatively and so flagging up a likely disease occurrence 5-7 days in advance may be invaluable as an early warning tool. With Red Thread and Dollar Spot for example, we know that these diseases respond to an N application, i.e you can grow them out…we know also they are probably encouraged by an over-regulated (from a PGR perspective) turf and primarily from a wet leaf surface. Reducing that leaf moisture may be a great way of changing the turf environment and swinging the balance away from this disease and therefore minimising surface disruption.

There’s a great (Syngenta) video of Paul Kerns talking about the model and how its used here

His comments on relative humidity are really interesting and apply in some part to Microdochium nivale however my disease modelling research has shown that M.nivale has different temperature thresholds (obviously) and grows faster over shorter humidity peaks….

OK that’s it for this week…

Catch you in a few weeks time…

Mark Hunt

 

 

 

 

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